Lubricant oil used for smoothing the operation of a head is applied on a medium of a hard disk drive (HDD) provided in a storage device. It has been known that, in accessing to the medium of the HDD, when only the outer side or inner side of the medium is used, a rut of the lubricant oil is likely to be generated between the inner side and the outer side.
When a rut is generated, errors in the head and the medium of the HDD drastically increase and become a cause of a failure in the HDD. Therefore, as a function of reducing the generation of a rut, a lubricant oil sweep function which is controlled in the HDD is used. The lubricant oil sweep function is a function of leveling the lubricant oil on the medium of the HDD. The lubricant oil sweep function is set effective or ineffective for each HDD, and when the function is set effective, a failure rate in the HDD may be reduced.
Japanese Laid-open Patent Publication No. 06-67812 describes the related technique.
However, there are cases where, when the lubricant oil sweep function is effective, a delay of response to a superordinate device occurs. That is, when the lubricant oil sweep function is effective in order to reduce the failure rate in an HDD, a delay of response to a superordinate device might not be avoided.
For example, when an access request from a superordinate device to an HDD and the lubricant oil sweep function in the HDD compete against one another, the access to the HDD stops. Then, after the operation of the lubricant oil sweep function ends, the access to the HDD which has stopped restarts, and the HDD returns a response to the superordinate device after the completion of the access thereto. While a response to write processing when the operation of the lubricant oil sweep function has not occurred is several milliseconds (ms), a response to write processing when the operation of the lubricant oil sweep function has occurred is 500 milliseconds (ms). Therefore, when the access to the HDD and the lubricant oil sweep function compete against one another, the delay of a response to the superordinate device is not avoided.
In a storage device in which a plurality of HDDs form RAID groups, when the operation of the lubricant oil sweep function occurs simultaneously in the HDDs in the same RAID group, an access stops in each of the HDDs which are operated, and thus, a delay of a response to the superordinate device is not avoided.
An advantage of some aspects of the present disclosure is that a technique for avoiding the delay of a response to a superordinate device may be achieved.